It is now widely recognized and accepted that release into the atmosphere of chlorofluorocarbon(CFC)-based and hydrochlorofluorocarbon(HCFC)-based refrigerants has a deleterious effect on the ozone layer that surrounds the earth. Production of CFC-based and HCFC-based refrigerants are to be severely curtailed in the future, and the cost of refrigerant for service purposes is already increasing. It has therefore become standard practice in the refrigeration system service industry to recover, recycle and reuse the refrigerant in the refrigeration system under service, or to recover, store and reclaim the refrigerant for later reuse, rather than merely to vent such refrigerant into the atmosphere and replace with new refrigerant as has been common practice in the past. U.S. Pat. Nos. 4,768,347, 4,805,416 and 4,878,356, all assigned to the assignee hereof, disclose equipment for recovering, recycling and/or recharging refrigerant in a refrigeration system service environment.
As currently envisioned R12 refrigerant is being replaced by different types of refrigerants in production of new refrigeration systems. For example, R12 refrigerant is being replaced by R134a refrigerant in the automotive industry--i.e., in automotive air conditioning systems. However, because these refrigerants and their associated lubricants are chemically incompatible with each other, inadvertent mixture of even small amounts of the different refrigerants can cause severe damage and early failure of the refrigeration system. It has been proposed to provide different service fittings on refrigeration equipment using different types of refrigerants, but the use of adapters and the like in the service industry may still result in inadvertent mixing of refrigerant/lubricant types, with consequent damage to the system under service and to the service equipment itself. A further complication arises with the use of intermediate refrigerants as substitutes for R12 refrigerant, such as ternary blends made by DuPont. With severe curtailment of R12 production in the future, it is anticipated that a significant number of refrigeration systems currently employing R12 refrigerant may eventually be retro-fitted with an intermediate substitute refrigerant. Inadvertent mixing of refrigerants is considered to be an irreversible process, leading to disposal of the mixed refrigerant as hazardous waste.
The various types of refrigerants therefore need to be kept separate to protect the integrity of the service equipment, and to ensure proper integrity and performance of the refrigeration equipment under service. Use of an incorrect refrigerant or an undesired mixture of refrigerants can occur due to improperly charging the incorrect refrigerant into the refrigeration equipment during installation or service, selective leakage or purging of one refrigerant component in a non-azeotropic refrigerant mixture, incomplete removal of the previous refrigerant in retro-fitting equipment or clearing of the recovery/recycling service system, chemical reaction within the refrigerant such as during a high temperature mechanical failure or hermetic compressor burnout generating undesirable refrigerant byproducts, or inadvertent mixing by recovery of refrigerant into an incorrect container or incorrect consolidation of recovered refrigerants into a larger container for shipment to a reclaim processing center.
In the past, refrigerant analysis has been accomplished by drawing a liquid refrigerant sample and sending the sample to a fully equipped refrigerant chemistry laboratory. An experienced chemist can remove some contaminants, such as oil, water and metallic particles, and then analyze the refrigerant using gas chromatography, mass spectroscopy or infrared spectroscopy. Air-Conditioning and Refrigeration Institute Standard 700-88 Specifications for Fluorocarbon Refrigerants specifies analysis of a liquid refrigerant sample. However, such laboratory analysis requires several hours or days to obtain, and is thus not suitable for use in the field. There is therefore a need in the refrigeration system service industry for a device that can be employed to test refrigerant in a storage container, or in a refrigeration system before performing service on the system, that is not restricted to any particular type of refrigerant or to automotive service applications, that is particularly well adapted to identify and distinguish between refrigerants of different types, that is inexpensive to manufacture and market, that is readily portable, that is rapid and efficient in operation, and/or that can be employed by relatively untrained service personnel.
U.S. Pat. No. 5,158,747 assigned to the assignee hereof discloses a device for identifying and distinguishing between and among refrigerants of different types. The device includes a fixed volume for containing a sample of refrigerant. The refrigerant to be tested is selectively admitted into the volume in vapor phase, vapor pressure of refrigerant within the fixed volume is measured, and admission of refrigerant is terminated when the vapor pressure of refrigerant contained in the volume reaches a preselected level. A sensor and associated electronics are coupled to the sample-containing volume for determining type of refrigerant vapor as a function of one or more selected properties of the refrigerant, and indicating such refrigerant type to an operator. U.S. application Ser. No. 08/047,263, also assigned to the assignee hereof, discloses an improved apparatus in which a thermistor provides a first electrical signal as a function of the combined effect of thermal conductivity and temperature of a refrigerant vapor sample in the sample-containing volume, and a temperature sensor provides a second electrical signal as a function of temperature of the refrigerant vapor sample essentially independent of thermal conductivity. Associated electronics determine type of refrigerant in the sample-containing volume as a function of the first and second electrical signals, and thus as a function of thermal conductivity of the refrigerant sample independent of sample temperature.
It has heretofore been proposed to employ near-infrared spectrophotometric analysis techniques for determining refrigerant make-up or composition. A liquid phase refrigerant sample is fed to a boiler, where the refrigerant sample is vaporized to separate refrigerant from oil and water. The refrigerant vapor is fed to a sample cell, where the vapor is condensed and subjected to near-infrared spectrophotometric analysis. Refrigerant make-up (i.e., refrigerant type or mixture of types) is determined by comparison of the near-infrared absorption spectra of the sample with prestored spectral data representative of known refrigerant types. Although the technique so proposed can provide an accurate indication of refrigerant type or types, improvements remain desirable. In particular, simplification is desirable to adapt the technique for use in the field. For example, the liquid phase refrigerant sample can contain up to twenty percent lubricant as well as dirt and metal particles, which can affect precision of the measurement process. The possible introduction of lubricant and particulates also necessitates cleaning of the test chamber or cell between uses.